PURPOSE: To generate variable torque transmitted from an input side to an output side by connecting an input shaft, an output shaft and a rotor of a rotatable fluid pump to a first, second and third rotating element of a planetary gear, respectively.

CONSTITUTION: Upon duty-control, a solenoid of a solenoid valve 5 acts as an orifice having an opening area according to a duty ratio. A suction port and a discharge port of each pump chamber 26 of a vane pump 4 are communicated with each other via the orifice. Torque is required for rotating a rotor 24. The torque corresponds to a discharge pressure of the pump chamber 26, i.e., the opening area of the orifice. A part of the torque of a rotary shaft 6 allows the rotor 24 of the vane pump 4 to be rotated via a sun gear 10, and the residual torque is transmitted to another rotary shaft 7. The sun gear 10 of a planetary gear 3 acts as a reaction element. Therefore, a change in duty ratio of the solenoid valve 5 enables the torque transmitted from an input side to an output side to be arbitrarily controlled.